Linearity compensation method and related acoustic system

Abstract

A linearity compensation method for a sound producing device (SPD) includes steps of: applying a test signal on a first SPD; obtaining an acoustic measurement result generated from the first SPD according to the test signal; generating a compensation curve according to the acoustic measurement result; and performing a linearity compensation operation on a second SPD according to the compensation curve.

What is claimed is: 
     
       1. A linearity compensation method for a sound producing device (SPD), comprising:
 applying a test signal on a first SPD; 
 obtaining an acoustic measurement result generated from the first SPD according to the test signal; 
 generating a compensation curve according to the acoustic measurement result; and 
 performing a linearity compensation operation on a second SPD according to the compensation curve, to compensate for a linearity of the second SPD relative to a driving voltage for the second SPD. 
 
     
     
       2. The linearity compensation method of  claim 1 , wherein the step of obtaining the acoustic measurement result generated from the first SPD according to the test signal comprises:
 detecting a sound pressure level (SPL) of the first SPD when the first SPD receives the test signal. 
 
     
     
       3. The linearity compensation method of  claim 1 , wherein the test signal comprises a sine-wave signal carried on a plurality of voltages. 
     
     
       4. The linearity compensation method of  claim 3 , wherein the step of generating the compensation curve according to the acoustic measurement result comprises:
 measuring a plurality of SPLs of the first SPD corresponding to the plurality of voltages; 
 integrating the plurality of SPLs to generate a plurality of linearity data; and 
 generating a plurality of compensation data according to the plurality of linearity data; 
 wherein the plurality of compensation data construct the compensation curve. 
 
     
     
       5. The linearity compensation method of  claim 4 , wherein the step of performing the linearity compensation operation on the second SPD according to the compensation curve comprises:
 multiplying the driving voltage for the second SPD by one of the plurality of compensation data corresponding to the driving voltage to generate a linearity compensation voltage; and 
 outputting the linearity compensation voltage to drive the second SPD. 
 
     
     
       6. The linearity compensation method of  claim 4 , wherein the step of generating the plurality of compensation data according to the plurality of linearity data comprises:
 calculating a reciprocal of the plurality of linearity data to generate the plurality of compensation data. 
 
     
     
       7. The linearity compensation method of  claim 1 , wherein the compensation curve is obtained without measuring a mechanical characteristic of the first SPD. 
     
     
       8. A linearity compensation method for a sound producing device (SPD), comprising:
 generating a sensitivity curve comprising a plurality of sensitivity values for a first SPD; 
 integrating the plurality of sensitivity values to generate a plurality of linearity data; and 
 generating a plurality of compensation data according to the plurality of linearity data; 
 wherein the plurality of compensation data compensate for a linearity of a second SPD relative to a driving voltage for the second SPD. 
 
     
     
       9. The linearity compensation method of  claim 8 , wherein the step of generating the plurality of compensation data according to the plurality of linearity data comprises:
 calculating a reciprocal of the plurality of linearity data to generate the plurality of compensation data. 
 
     
     
       10. The linearity compensation method of  claim 8 , further comprising:
 performing a linearity compensation operation on the second SPD according to a compensation curve composed of the plurality of compensation data. 
 
     
     
       11. The linearity compensation method of  claim 10 , wherein the step of performing the linearity compensation operation on the second SPD according to the compensation curve composed of the plurality of compensation data comprises:
 multiplying the driving voltage for the second SPD by one of the plurality of compensation data corresponding to the driving voltage to generate a linearity compensation voltage; and 
 outputting the linearity compensation voltage to drive the second SPD. 
 
     
     
       12. The linearity compensation method of  claim 8 , wherein the plurality of sensitivity values comprise a plurality of sound pressure levels (SPLs) of the first SPD under a test signal. 
     
     
       13. The linearity compensation method of  claim 8 , wherein the plurality of compensation data are obtained without measuring a mechanical characteristic of the first SPD. 
     
     
       14. An acoustic system, configured to drive a first sound producing device (SPD), the acoustic system comprising:
 a memory, configured to store a plurality of compensation data; and 
 a computation circuit, coupled to the memory, configured to receive a driving voltage for the first SPD, and compute a compensated voltage according to the driving voltage and a compensation data of the plurality of compensation data corresponding to the driving voltage; 
 wherein the plurality of compensation data are comprised in a compensation curve generated according to an acoustic measurement result; 
 wherein the acoustic measurement result is generated from a second SPD by applying a test signal on the second SPD; 
 wherein the plurality of compensation data compensate for a linearity of the first SPD relative to the driving voltage for the first SPD. 
 
     
     
       15. The acoustic system of  claim 14 , further comprising:
 a power amplifier, coupled to the computation circuit and the first SPD, configured to output a linearity compensation voltage corresponding to the compensated voltage to drive the first SPD. 
 
     
     
       16. The acoustic system of  claim 14 , wherein the acoustic measurement result comprises a sound pressure level (SPL) of the second SPD. 
     
     
       17. The acoustic system of  claim 14 , wherein the compensation curve is generated without measuring a mechanical characteristic of the second SPD. 
     
     
       18. The acoustic system of  claim 14 , wherein the computation circuit comprises a multiplier, and the multiplier is configured to multiply the driving voltage by the compensation data. 
     
     
       19. The acoustic system of  claim 14 , wherein the compensation curve is generated by performing the following steps:
 measuring a plurality of SPLs of the second SPD corresponding to a plurality of voltages; 
 integrating the plurality of SPLs to generate a plurality of linearity data; and 
 generating the plurality of compensation data of the compensation curve. 
 
     
     
       20. The acoustic system of  claim 19 , wherein the compensation curve is generated by further performing the following steps:
 calculating a reciprocal of the plurality of linearity data to generate the plurality of compensation data of the compensation curve. 
 
     
     
       21. The acoustic system of  claim 14 , further comprising:
 a feedback circuit, configured to compensate for a voltage drift of the compensation curve. 
 
     
     
       22. The acoustic system of  claim 21 , wherein the feedback circuit comprises:
 a low-pass filter, configured to output a frequency corresponding to the voltage drift; and 
 a gain amplifier and an adder, coupled to the low-pass filter, configured to improve a stability of the acoustic system and compensate for the voltage drift. 
 
     
     
       23. The acoustic system of  claim 21 , wherein the voltage drift is generated from an alternating current (AC) coupling in the acoustic system.